This invention relates to the lining of pipelines and passageways, wherein a lining tube is applied to the pipeline or passageway surface, and on completion of the lining operation remains in this position so as in effect to resurface the passageway. The lining may serve any of a number of functions, for example structurally to enhance the pipeline or passageway, to act as a barrier to liquid ingress or egress in relation to the passageway, to restore the flow characteristics of the passageway and to enhance the pipeline or passageway for carrying an alternative medium, for example to enable a pipeline or passageway to carry a corrosive medium where before its surface was unsuitable for carrying such medium. The lining may of course perform any combination of these functions and there may also be additional functions which it can perform.
Many, and probably the majority of these pipelines or passageways, have what are called lateral connections, being connections to spur or feeder pipes or passageways which branch from the main pipeline or passageway. In the case of a sewer the lateral connections typically are the individual waste pipe connections to individual homes and other buildings used by the public.
One of the problems concerned with the lining of underground pipelines or passageways which have lateral connections, is that when the lining is placed in position, it is not possible, beforehand, to make cut outs which will register with the lateral connections, and it is usual therefore for the lining tube to extend over the lateral connections, and subsequently to cut the tube at locations in register with the lateral connections to re-establish these connections. This cutting is done by placing in the lined pipeline or passageway a cutting device which is moved so as to register with the lateral connection, and to cut the lining to re-establish the lateral connection.
The difficulty which one experiences in the operation is the accurate placement of the cutting apparatus for the location of the lateral connection as it is covered by the lining. It is known to insert a T.V. camera to inspect the pipeline or passageway before lining takes place, to locate and record the positions of the lateral connections, and it is also known to transport an inspection camera through the pipeline or passageway after the lining operation in order visually to examine the lining, because if, as is frequently adopted, the lining is placed in position by the use of fluid pressure, and the lining is at least initially flexible, as it is urged into position, those portions of the lining in register with the lateral connections deflect into the laterals and so "dimples" are formed in the lining at the lateral connection locations. The camera can often see these "dimples" as distinct depressions which cast shadows. An operator at ground level with a T.V. monitor therefore is able to see the "dimple", and by appropriate controls which are to hand, he can manipulate the cutter to cut the lining and re-establish the lateral connection.
In practice this operation is very difficult. In the first place, using the method of pre-locating and recording the position of each lateral is not sufficiently accurate, so that often laterals cannot be re-located. In the post location of lateral connections frequently the dimples cannot be easily seen if as again frequently happens, the lining does not deflect to form the "dimples" referred to above, and the laterals may not be found after lining.
Obviously, and especially in the case of sewer pipes, if the laterals cannot be found and are not re-established, then serious problems will result. Although contractors who perform the lining operations and re-establishment of lateral connections do eventually succeed in performing contracts, there is considerable room for improvement in the aspect of the lining operation involving the accurate location of the lateral connections and the reliable re-establishment of these connections.
In the UK Patent Application No 2157796A it has been proposed that by means of a suitable apparatus, magnetically sensitive means is positioned on the pipeline or passageway before the lining operation, at a pre-determined distance from the lateral connection, and following the lining operation, means is inserted in the lined passageway by which the location of the deposit can be radiation sensed.
The magnetically sensitive means is a spot or blob of paint or paste applied to the pipeline or passageway surface which is applied by observation using a television camera. This can lead to difficulties insofar as conditions in a sewer are not always ideal for accurate working and it is desirable that the marking should be accurately placed in a simple and effective manner.
The present invention seeks to provide a simple but effective method and means for the said effective placement of said markings.